In recent years, quality of image and video becomes high rapidly, and thus the quantity of information to be dealt with by a user increases more and more. For this reason, various techniques for increasing surface recording density are examined and investigated for enlarging the capacity of a magnetic recording apparatus which is called an HDD (hard disk drive). As one of promising techniques for achieving such high-density magnetic recording, there is a shingle recording method as disclosed in PTL 1 which records a recording column such that the recorded recording column partially overlaps a recording column which is adjacent to the recorded recording column in the width direction of a track and was recorded immediately before.
In general, the pitch of a track to be formed on a magnetic recording medium is about several times longer than the length of a formed shortest mark. However, in the shingle recording method, since the recording column is recorded so as to partially overlap the adjacent recording column recorded immediately before, it is possible to shorten the pitch of the finally formed track to the extent of the length of the shortest mark. That is, since the recording is performed such that the recorded recording column partially overlaps the adjacent recording column recorded immediately before, the number of tracks per unit length becomes several times, so that it is possible to highly improve recording density.
Besides, in a case where the data recorded on the HDD is deleted, such deletion is generally performed by using a deleting command, a deleting operation and the like installed in the HOD. However, in such a deleting method, merely the data at the storage position indicated by a file system is deleted. That is, since the data themselves recorded on the magnetic recording medium such as the HDD are not deleted, these data still remain.
For this reason, it is possible to read the deleted data by a method of directly accessing the relevant data on the HDD without using the file system or a method of using a data recovery tool.
Under these circumstances, from a viewpoint of prevention of information leakage, complete deletion to the data remaining on the HDD is performed recently. Here, it should be noted that the complete deletion can be rephrased as a deleting method of deleting the original data from the magnetic recording medium by overwriting meaningless data entirely to the area on the magnetic recording medium at which the original data intended to be deleted have been recorded.